Messenger is a JMS facade and connection/session pool API to make using JMS much easier.

JMS uses both Connection objects and Session objects along with MessageConsumer and MessageProducer objects making it harder than you might imagine to use it properly in a multi-threaded environment.

In addition JMS has lots of different factory methods for creating connections, sessions, producers, consumers - much of which should really be deployment time configuration details.

So Messenger abstracts this away into a simple Facade pattern.